Carton

ABSTRACT

The present invention concerns a carton for holding granular or other products in a bag. The carton comprises a substantially rectangular sleeve having front, rear and side panels ( 1, 2, 3 ). The front and rear panels have flaps ( 21, 22 ) which resiliently engage within a channel ( 20 ) formed when the side panels ( 3 ) are deformed inwardly along crease patterns ( 5 ), the resulting inter-engagement of components holding the top of the carton securely together. A bag is secured and sealed internally of the carton by being located under one of the flaps ( 22 ) which is biased to clamp the bag.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International ApplicationNo. PCT/GB2003/004825.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a carton for holding products such ascereal. There are many types of carton and each one must be carefullydesigned and prepared for its particular application. Cartons areusually made up from a blank, which can be made from a planar materialsuch as cardboard or a malleable plastic for example acetate.

2. Description of Related Art

Conventionally, cereals and other dry granular or grain-like productsare sold, for example, by establishments such as supermarkets and highstreet retail outlets in standard rectangular shaped cardboard cartonswhere the product inside the carton is contained in a sealed air-tightbag.

The carton usually contains numerous servings. In a household, servingsare dispensed over a period of time from the initial opening of thecarton, the remainder of the pack being put away until the next time theproduct is desired. For example a carton containing 12 servings may lasta family 2 weeks during which the carton is opened and closed severaltimes.

In order to re-close such cartons, they typically have a pair ofopposing lid flaps, provided with a tab and opposing slot arrangement.After an initial opening, the tab on one of the flaps can be slid intothe slot provided in the other flap to engage the two together and closethe top of the carton.

Many families eat cereal for breakfast such that very high volumes ofsuch cartons are produced. For this reason (and for hygiene) it iscommon for these cartons to be automatically packed on a machine packingline. It is also for this reason that the cartons tend to be purchasedby the cereal manufacturer at very economical prices and have beendesigned to use the minimum of raw material possible.

Machine packing lines are designed to run large volumes of productsoften working on a 24 hour basis. It is unusual for the cerealmanufacturers or their engineers to want to adjust the machines toaccommodate different styles or constructions and many machine packinglines are designed to accept only one size and style of carton. In thisconnection, it is common to see different surface print designs ofcartons.

There are several disadvantages associated with the typical cardboardcereal carton. Firstly, the re-closing mechanism on the carton tends notto work particularly well as the tab and slot engage only to a limitedextent. The demand for economy in the carton does not in this regardhowever allow for additional material to be utilised to make asatisfactory closure mechanism.

Secondly, the bag (which holds the cereal) is not securely held closedwithin the carton once opened and tends to unravel itself and leave thecontents open to the environment. Consequently there is degradation inthe quality of the product with regard to freshness. For example, acereal will lose its “crispness”. This will happen after the carton hasbeen opened and is being stored in the kitchen cupboard, which is not anairtight location.

A third disadvantage is a result of the combination of the previouslymentioned two problems. If the carton is knocked over, for examplewhilst on the breakfast table, it is likely that the product will fallout. The current designs are not generally “spill-proof”.

It is recognised by the breakfast cereal industry that a betterre-closure of the carton and the bag is high on the list of consumerrequirements.

There have been various attempts to create a better re-closure on astandard cereal carton. For example U.S. Pat. No. 2,789,751 discloses are-closable carton for packaging breakfast foods, and U.S. Pat. No.2,345,486 discloses another re-closable carton for packaging breakfastfoods. Both of these packs use a “tab and slot” arrangement to re-closethe pack. A disadvantage of such tab and slot arrangements is that oncethe tab is entered into the slot and then subsequently removed, theclosure tends to fail on further use. This is because any minimal wearor damage to the tab or slot stops it performing.

Another disadvantage of such arrangements is that the closure mechanismcovers up a certain amount of decoration area that can be printed on thesurface of the pack. This area is viewed as valuable for advertising anda further disadvantage of the tab and slot closure arrangement is that aslot hole has to be cut into the advertising area.

Moreover, cuts and slots in various areas are disadvantageous to thestrength and integrity of the carton. Cuts and slots in the outside ofpacks are furthermore not desirable to retailers and manufacturersbecause they are not “tamper-evident”.

U.S. Pat. No. 2,178,730 discloses a carton having a top which is formedof two top flaps which each extend across the whole of the top of thecarton. To re-close the carton, this top has to be cut along three sidesof the carton and then folded into the interior, with the side panelshaving been deformed inwardly. The requirement of cutting the top flapis burdensome on the user. Moreover, the carton requires relativelylarge amounts of material in its manufacture, since the top flaps mustspan the entire top of the carton.

EP0 639 512 discloses a carton having top flaps which fold into theinterior of the carton, the carton sides being collapsible inwardly tocreate a recess in the top of the carton into which the flaps aredirected, the inserted flaps being biassed against one another toprevent them coming out of the recess. The top flaps of this carton arecut away at their sides to prevent the flaps being distorted as theyenter the recess. This arrangement however suffers from the problem thatrepeated use of the carton rapidly reduces the effectiveness of there-closure mechanism, in that once inserted into and then removed fromthe recess the flaps lose their resiliency. It is this resiliency whichbiasses the flaps against one another and thereby holds the carton in aclosed position.

SUMMARY OF THE INVENTION

The present invention seeks to provide a carton that can overcome theaforementioned disadvantages. Whilst this style of construction isperfectly suited to the current market for cereal packaging there arevarious other end uses for which it is suited.

According to a first aspect of the present invention, there is provideda reclosable carton comprising front, rear and side panels; the sidepanels being configured to deform when the front and rear panels arebrought together, such that one or more holding areas are createdbetween an inside face of a side panel and an inside face of one of thefront or rear panels, the one or more holding areas having an increasedholding effect as the front and rear panels are brought closer together,wherein the front and rear panels are each provided with a flap at a topportion thereof, and wherein in a reclosure operation, the front andrear panels are movable together and the front and rear panel flaps arepositionable in a common one of said holding areas; at least one of saidfront and rear panel flaps having an interference fit with said commonholding area.

In this way, a re-closure mechanism is formed from the engagement of thefront and rear panel flaps in a holding area formed between one of thefront and rear panel flaps and the deformed side panels. In this regard,the front and rear panel flaps may be resiliently biased against beingfolded into the interior of the carton. Hence, when inserted into thechannel the front and rear panel flaps are urged against one another,increasing the friction there-between and thereby enhancing the securityof the re-closure mechanism.

Preferably, the side panels are configured to deform inwardly, such thatthe reclosure mechanism is provided inwardly of the carton.

The one or more holding areas may further each comprise a deformed sidepanel flap folded into the interior of the carton. This assists inenhancing the holding action of the holding area on the front and rearpanel flaps.

The interference fit of the at least one of the front and rear panelflaps with the holding areas can be provided where its edges engage withthe one or more holding areas.

In this respect, the at least one of the front and rear panel flaps hassubstantially the same width as a width of the panel from which itextends.

This said, the at least one of the front and rear panel flaps can beprovided with a slight taper to gradually increase the extent ofinterference fit and hence holding action of the holding areas as it isintroduced into the holding areas.

The at least one of the front and rear panel flaps may have a line ofweakness across its width, extending parallel with a top edge of saidpanel from which it is provided. This line of weakness allows the flapto be folded for its facilitating insertion.

Conveniently, said flaps are foldable into the interior of the carton tothereby form, in association with the front, rear and side panels, twointernal compartments at the top of the carton, the flaps being biasedagainst one another when folded into the interior of the carton tothereby promote resistance to the flaps being removed from the top ofthe carton.

The internal compartments have two main functions. The function of asmaller one of the compartments is to hold an open liner bag closed. Thefunction of both compartments is to generally seal the internalenvironment of the carton. In closing both the bag and the carton, airis prevented from reaching the product and hence the product retains itsfreshness for a longer period.

The carton may comprise a substantially rectangular tube.

Conveniently, the side panels of the carton are each provided with ascore pattern extending downwardly from their top. The score pattern mayin this regard comprise a vertical score line extending downwardly fromthe top of the carton substantially parallel with the vertical sides ofthe side panel, and a substantially triangular score line whose top apexconnects with the vertical score line, the remaining corners of thetriangular score line terminating at the vertical sides of the sidepanel. The substantially triangular score line may comprise arcuatesides.

When folded into the interior of the carton, the side panel flapspromote the overall stiffness of the top of the carton, and alsoadditionally urge the respective components into inter-engagementthereby increasing the friction within the closure arrangement andfurther increasing the resistance to the flaps becoming released fromthe top of the carton.

The side panel flaps can be provided with a score pattern which overliesthat of the side panels when folded into the interior of the cartonagainst the inside surface of the side panel.

The present invention further comprises a reclosable carton comprisingfront and rear panels connected by side panels, the front and rearpanels having flaps at their top portions; wherein an upper portion ofeach side panel is formed to be deformable from an open position of thecarton to a closed position of the carton against an opening force, theside panels in the closed position defining a holding channel togetherwith one of the front and rear panel flaps; and wherein the other of thefront and rear panel flaps is insertable into the channel and engagesthe said one of the front and rear panel flaps, the flaps being biassedinto engagement with one another and further being held within theholding channel through a clamping action of the channel on edgeportions of the flaps.

Conveniently, the carton has means for affixing a surface of a liner bagin position at or adjacent said first one of said front and rear panelflaps.

According to a further aspect of the present invention there is provideda blank for use in forming a carton comprising:- front and rear panels,and a pair of side panels; wherein the front and rear panels are eachprovided with a flap at a top end thereof, the side panels having ascore pattern enabling the side panels to deform to form a channel withone of said front and rear panel flaps, when folded into the interior ofthe carton, the other of the front and rear panel flaps being configuredto be clamped at edge portions thereof when inserted in the channel andwhen the front and rear panels are brought together.

The score pattern may comprise a vertical score line extendingdownwardly from a top of the side panel substantially parallel with thevertical sides of the side panel, and a substantially triangular scoreline whose apex connects with the vertical score line, the remainingcorners of the triangular score line terminating at the vertical sidesof the side panel. The sides of the triangular score line may bearcuate.

The other of said front and rear panel flaps may have a score lineextending parallel with a top edge of said front or rear panel.

The other of said front and rear panel flaps can moreover be sized toengage with an interference fit in said channel.

Each side panel may further be provided with a side panel flap at itsupper portion.

The present invention can thus provide a carton whereby a smaller one oftwo compartments can be used to secure the open top of a bag (containingthe product) by the front and rear panel flaps and the side wall of thecompartment pressing the two sides of the bag together and holding itclosed. The configuration of the re-closing device creates a cartonwhich will not open unless specifically opened, even if it is knockedover and is therefore “spill-proof”. The configuration changes the shapeof the carton from rectangular to “house-shaped”, i.e. a structurehaving a top resembling a tapered roof. This appearance is pleasing tothe eye.

As all the elements of the re-closure device are internal and can bemade with no cuts or slots in any of the panels, the advertisingabilities of the main panels are not diminished. Similarly the strengthand integrity of the carton is maintained during manufacturing, machinepacking and delivery processes.

The flaps provided to the front, rear and side panels can be formed fromthe same four panels that form the top of the rectangular box in themachine packing process. General wear and tear or minor damage to flapsdoes not impair the performance of the re-closure device over the lifespan of the carton.

The structure forming the compartments makes a strong closure. Thismakes the carton “spill-proof”. “Spill-proof” in this instance beingdefined as preventing product from falling or running out the carton dueto accidental events such as knocking over. This feature of the designis desirable and may be required by companies or individuals where theproduct is not held in a bag.

The present invention requires no additional material to make there-closure device. The “extra material” utilised is created by thecompression or deformation of the two side panels.

The present invention operates whether the overlap of the top panelflaps of the carton is minimal or full and can be used on a variety ofdifferent sizes of carton.

The present invention will operate on existing packing lines with littleor no modification. This is beneficial to many manufacturers, who mayhave several factories worldwide, as there is little or no costassociated with implementing the present invention worldwide. The costimplications are within the tooling for carton manufacture and areminimal.

The design of the closure mechanism can determine whether the frontpanel flap folds in last or whether the rear panel flap folds in last orcan be constructed so that either engaging member can be chosen to foldin last. This has no effect on the forming of the compartments. Thisdecision is the responsibility of the carton purchaser (productmanufacturer) in instructing the carton manufacturer to produce thetooling accordingly.

As there are no slots or cuts in the outside walls of the carton in theretail outlets the pack is “tamper-proof”.

The present invention can be printed according to existing methods.

The present invention also provides a blank for forming the cartonaccording to the present invention. The present invention is formed fromthe blank as is conventional by joining various areas of the cartonblank to each other. This can occur both in carton manufacture andmachine packing.

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a blank of the present invention;

FIG. 2 shows an external view of a carton formed from the blank shown inFIG. 1;

FIG. 3 shows a diagrammatic view of the formed carton showing all mainpanels (including those which cannot be seen from the front) formed fromthe blank shown in FIG. 1;

FIG. 4 shows a plan top view of the carton shown in FIGS. 2 and 3 onceit has been originally opened;

FIG. 5 shows a plan top view of the carton shown in FIG. 4 undergoing are-closing operation;

FIG. 6 shows a perspective view of the carton after it has beenoriginally opened and then re-closed;

FIG. 7 shows an internal plan view from underneath of the carton showingthe inside components of the top portion of the carton in a re-closedstate;

FIG. 8 shows a plan view of an alternative carton blank;

FIG. 9 shows a plan view of an alternative carton blank;

FIG. 10 shows a perspective view of the carton of the present inventionpartially into the re-closure operation; and

FIG. 11 shows a perspective view of the carton of the present inventionon completion of the re-closure operation.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a blank 100 of the present invention is formed froma planar sheet of solid board cardboard (or acetate/plastic) andcomprises four main panels, including a front panel 1, a rear panel 2and two side panels 3. At the top portion of these panels are providedassociated flaps 21, 22, 23 and 23 which form four engaging members ofthe reclosure device and the top of the carton.

The base of the carton is formed from four flaps 7. A glue seam 4 on theside facilitates formation of the carton 200 from the blank 100 as shownin FIG. 2.

Flaps 21, 22, 23 and 23 are shown in FIG. 1 in an unfolded position. Inthis regard, flap 21 has a crease 11 along its width to facilitatere-closure of the carton. The crease allows the flap 21 to be bent overand thereby be angled favourably for insertion into the carton asdescribed more fully below.

Flaps 23 are creased with a score pattern 10 as shown in FIG. 1, toallow inward folding, following a crease or score pattern 5 afforded tothe collapsible or compressible side panels.

The crease pattern 5 on the relatively narrow side panels 3 allows thecarton to deform at the top, into the shape required for the re-closure.In particular, the top portion of the side panels can deform inwardly asshown in FIGS. 4 and 5, and as described more fully below.

The creases 5 may be straight or curved as shown in the figures. Theglue seam 4 can itself include a score pattern adjustment 6 to allow thecarton to fold at this point easily. It will be understood that thecreases shown could be replaced by combinations of scores or cuts toassist make up.

A carton 200 of the present invention formed from the blank 100 shown inFIG. 1, is shown in FIGS. 2 and 3 and is initially prepared from theblank 100 as follows.

As shown in FIG. 3, the flaps 21, 22, 23, 23 and the base 7 are foldedinwards at 90 degrees along crease lines 8 and 9 and fixed, for example,by gluing forming a rectangular carton. This is the configuration inwhich the carton with product inside in intended to be initially sold.

FIG. 4 shows a view looking into the top of the carton once it has beeninitially opened. Front and rear panel flaps 21 and 22 have been foldedoutwards and downwards, and flaps 23 are at 90 degrees to the cartonsides 3.

FIG. 5 shows the commencement of make up of the re-closure device. Rearpanel flap 22 now is folded inward across crease 8 so that it projectsdownwardly into the interior of the carton. It is arranged to face theinside surface of the adjacent rear panel 2.

In this way, and as shown in FIGS. 7 and 10, there is formed a firstcompartment 17 between the rear panel 2 and the rear panel flap 22. Thiscompartment is used to cover the top portion of a bag (provided withinthe interior of the carton for holding product) in use. In this respect,side panel flaps 23 are shown folded inward across crease 13 against theinside surface of the side panels 3.

As shown in FIG. 10, the side panels 3 at the top of the carton arepushed inwards according to the configuration of creases 5. The top ofthe carton is shown as being compressed or collapsed together. Tore-close the carton, front panel flap 21 is pushed into a channel orapertures 20 defined by the deformed side panels 3 and their flaps 23and the inwardly folded rear panel flap 22. In FIG. 10 the rear panelflap 22 and the lower portion of the front panel flap 21 are shown inphantom lines as they would not be visible, being within the interior ofthe carton. The crease 11 on the front panel flap 21 allows the leadingedge of the flap 21 to be angled for insertion into the channel 20.

When front panel flap 21 is pressed fully into the channel 20, thecarton 300 shown in FIG. 6 is formed.

As shown in FIGS. 1, 8 and 9, the width of the front panel flap 21 issubstantially the same as the width of the top of the front panel, suchthat the edges of the front panel flap 25 extend at substantially atright angles from the top edge of the front panel 26. As a result, asthe front panel flap is urged into the channel 20, it will engage andinterfere at its edges 25 with the channel. There is hence a deliberatedistortional force on the front panel flap as it is urged into thechannel. As the internal faces of the channel come together and thefront panel flap is moved further into the channel, the edges of thefront panel flap will become clamped by the channel.

The front panel flap can have a slight tapered profile, to afford anprogressively increased “interference-fit” with the channel 20 as thetop edges of the front and rear panels are brought to be adjacent oneanother when the carton is re-closed. Hence, when the front panel flap21 is pushed in fully, a clamping “interference-fit” is attained betweenits edges and the channel, the front panel flap being wedged in positionat that point against the opening force of the deformed side panels 3.The folded over side panel flaps assist in ensuring a clampinginterference fit. As shown in FIG. 11, edges 25 the front panel flap 21extend down along edges 27 of the channel 20, where they are heldsecurely.

A second relatively larger compartment 16 is formed in the interior ofthe carton, and is defined by a top portion of the front panel 1, theinside surface of the front panel flap 21 and the deformed side panelsflaps 23.

In this regard, the deformed side panel flaps 23 and side panels act asabutment surfaces which project into the larger compartment 16.

FIG. 6 hence shows a view of the outside of the carton 300 havingundergone the re-closure operation. All flaps 21, 22, 23 and 23 arefolded internally within the top of the carton and the carton is held ina secure formation. The combination of the flaps 21, 22, 23 and 23pressing against each other together with the side panels 3 deformed attheir top according to crease pattern 5 generates cooperating andopposing forces for assisting in securing the reclosure device closed.The pack also provides a pleasing aesthetic appearance. Moreover theclamping action afforded by the holding channel 20 on the edge portionsof the front panel flap 21 ensures a reliable and re-usable closingmechanism.

Referring to FIG. 7 there is shown an internal view of the made upcarton 300 shown in FIG. 6 from the blank 100 shown in FIG. 1. The baseis shown folded back along crease lines 9 to show the formation of there-closure device at the top of the pack. The side panels 3 of thecarton are compressed and shaped according to the crease lines 5 oneither side. Side panel flaps 3 have a crease pattern 10 that overliesthe shape of crease pattern 5. The two compartments formed 16 and 17 areon either side of the touching engaging flaps 21 and 22. The smaller ofthe compartments 17 can be used to compress the sides of an open bagtogether to thereby seal the bag. In order to assist in the location ofsuch a bag under the flap 22, the bag may be affixed to the insidesurface of the carton at a position which will locate under the flap 22.For example a line of suitable adhesive running parallel to the top edgeof panel 2 may be used to fix one side of the bag in the carton. Theline of adhesive may further create a raised ridge which can assist topinch the bag to seal it when the carton is re-closed.

FIG. 8 shows a plan view of an alternative carton blank 400 where eitherengaging flaps 18 or 19 can be folded in first. In this embodiment bothengaging flaps have the characteristics to perform the functions ofeither of the flaps 21 or 22 as shown in FIGS. 1 to 7.

FIG. 9 shows a plan view of an alternative blank 500 where glue seam 4is attached to side panel 15. The blank 500 is substantially identicalto the blank 100 shown in FIG. 1.

In preferred embodiments of the present invention, the blanks 100, 500,400 and cartons 200, 300 will have printed material on the outersurface.

It will be understood that the embodiments illustrated describe theinvention only for the purpose of illustration. In practice, theinvention may be applied to many different configurations, the detailedembodiments being straightforward for those skilled in the art toimplement.

1. A reclosable carton comprising: front, rear and side panels, the sidepanels being configured to deform when the front and rear panels arebrought together, such that one or more holding areas are createdbetween an inside face of a side panel and an inside face of one of thefront or rear panels, the one or more holding areas having an increasedholding effect as the front and rear panels are brought closer together,wherein the front and rear panels are each provided with a flap at a topportion thereof, wherein, in a reclosure operation, the front and rearpanels are movable together and the flaps are positionable in a commonone of said holding areas, and wherein at least one of said flaps havingan interference fit with said common holding area.
 2. A reclosablecarton according to claim 1, wherein the side panels are configured todeform inwardly.
 3. A reclosable carton according to claim 1, whereinsaid one or more holding areas each further comprises one of said frontand rear panel flaps when folded into the carton.
 4. A reclosable cartonaccording to claim 3, wherein said one or more holding areas eachfurther comprises a deformed side panel flap folded into the interior ofthe carton.
 5. A reclosable carton according to claim 4, wherein theother of the front and rear panel flaps has, at its edges, aninterference fit with the one or more holding areas.
 6. A reclosablecarton according to claim 5, wherein side edges of other of the frontand rear panel flaps are substantially normal to a top edge of the panelfrom which they extend.
 7. A reclosable carton according to claim 6,wherein the other of the front and rear panel flaps has a marginaltaper.
 8. A reclosable carton according to claim 5, wherein the other ofthe front and rear panel flaps has a line of weakness extending parallelwith a top edge of said panel from which it extends.
 9. A reclosablecarton according to claim 1, wherein said flaps are foldable into theinterior of the carton to thereby form, in association with the front,rear and side panels, two internal compartments at the top of thecarton.
 10. A reclosable carton according to claim 1, wherein the cartoncomprises a substantially rectangular tube.
 11. A reclosable cartonaccording to claim 1, wherein the sides of the carton are each providedwith a score pattern extending downwardly from their top.
 12. Areclosable carton according to claim 11, wherein the score patterncomprises a vertical score line extending downwardly from the top of thecarton substantially parallel with the vertical sides of the side panel,and a substantially triangular score line whose top apex connects withthe vertical score line, the remaining corners of the triangular scoreline terminating at the vertical sides of the side panel.
 13. Areclosable carton according to claim 12, wherein the sides of thesubstantially triangular score line are arcuate.
 14. A reclosable cartonaccording to claim 11, wherein side panel flaps on the sides of thecarton have a score pattern which overlies the score pattern of the sidepanels when folded into the interior of the carton.
 15. A reclosablecarton according to claim 1, wherein the carton has means for affixing asurface of a liner bag in position at or adjacent said first one of saidfront and rear panel flaps.
 16. A reclosable carton comprising: frontand rear panels connected by side panels, the front and rear panelshaving flaps at their top portions; wherein an upper portion of eachside panel is formed to be deformable from an open position of thecarton to a closed position of the carton against an opening force, theside panels in the closed position defining a holding channel togetherwith one of the front and rear panel flaps; and wherein the other of thefront and rear panel flaps is insertable into the channel and engagesone of the front and rear panel flaps, the flaps being biased intoengagement with one another and being held within the holding channelthrough a clamping action of the channel on edge portions of the flaps.17. A reclosable carton according to claim 16, wherein the other of thefront and rear panel flaps has a tapered profile to increase the degreeof interference fit as the other of the front and rear panel flaps isinserted further into the holding channel.
 18. A reclosable cartonaccording to claim 16, wherein each side panel has a flap at its upperportion, which is positionable in the interior of the carton to assistin the clamping engagement of the front and rear panel flaps.
 19. Ablank for use in forming a carton comprising: front and rear panels; anda pair of side panels, wherein the front and rear panels are eachprovided with a flap at a top end thereof, the side panels having ascore pattern enabling the side panels to deform to form a channel withone of said front and rear panel flaps when folded into the interior ofthe carton, and the other of the front and rear panel flaps isconfigured to be clamped at edge portions thereof when inserted in thechannel and when the front and rear panels are brought together.
 20. Ablank according to claim 19, wherein the score pattern comprises avertical score line extending downwardly from a top of the side panelsubstantially parallel with the vertical sides of the side panel, and asubstantially triangular score line whose apex connects with thevertical score line, the remaining corners of the triangular score lineterminating at the vertical sides of the side panel.
 21. A blankaccording to claim 19, wherein the other of said front and rear panelflaps has a score line extending parallel with a top edge of said frontor rear panel.
 22. A blank according to claim 19, wherein the other ofsaid front and rear panel flaps is sized to engage with an interferencefit in said channel.
 23. A blank according to claim 19, wherein eachside panel is provided with a side panel flap at its upper portion.